Call detail record (CDR) is a report that telephone exchanges generated, which contains detailed information about calls originating from, terminating at or passing through the exchange. CDRs are used mainly for billing purpose. A call detail record is a data record that contains information related to a telephone call, such as the origination and destination addresses of the call, the time when the call started and ended, the duration of the call, the time of day the call was made and any toll charges that were added through the network or charges for operator services, among other details of the call. CDR data fields are fully populated when the underlying call/transaction ends. The CDR is an asset in managing long distance telephone costs and aids in the planning for future telecommunications needs.
Most telephone PBX (public branch exchange) and PMS (property management systems) output CDR. Generally, these get created at the end of a call but on some phone systems the data is available during the call. This data is output from the phone system by a serial link known as the Station Message Detail Recording port (SMDR).
At present, some billing centers need to delete the original CDR file after transferred successfully from wireless call server (WCS). Thus, the normal active/standby equipment synchronization mechanism may meet problem. For example, the active equipment has file 1 and file 2, and transfers file 1 to a billing center; the billing center deletes the transferred file 1 to mark that file 1 is transferred successfully. Note that, file 1 still exists in the standby equipment. If the active/standby equipment uses the normal synchronization mechanism, then the standby equipment will think file 1 is missed in the active equipment and copy file 1 to the active equipment. The result is that the billing center will misunderstand file 1 is not transferred successfully. This conflict with billing center transfer mechanism (transfer and delete).
FIG. 1 show an existing solution for synchronous double backup with active/standby mechanism. As shown in FIG. 1, the active file handling device 1 copies the CDR file from file set A1 to B1, A1 being a backup of B1, and the standby file handling device 2 copies the CDR file from file set A2 to B2, A2 being a back up of B2. The billing center gets files from B1 or B2 and then deletes those files in B1 and B2 after transferred successfully. For synchronization between A1 and A2, if the standby file handling device 2 finds that the active file handling device 1 misses file, then it will copy the backup file to the active file handling device 1 in order to ensure file sets A1 and A2 are synchronized. For synchronization between B1 and B2, if the standby file handling device 2 finds that the active file handling device 1 misses file for a while (for example 30 minutes), then it will deletes the backup file B2 in order to ensure file sets B1 and B2 are synchronized.
It means the synchronization between A1&A2 and B1&B2 are different, it will make the system more complicate and consume more system resource.
Therefore, it is necessary to find a new method to fulfill the following two requirements:                ensure that the billing center may delete the original CDR file after transferred from the WCS successfully;        ensure that the WCS has the CDR file backup after transferred.        